In recent years, marine resource exploration equipments and undersea earthquake sensor networks for early earthquake detection are becoming widespread, and there is an increased demand for a device for supplying electric power to these equipments. The device for supplying electric power needs to use a wireless power transmission technique that enables efficient power transmission even in seawater, because the surrounding area of the device is seawater. The wireless power transmission technique needs to be a technique that does not require the power supply metal plugs to be exposed, and that has no possibility of shorting even in seawater, which has an electric conductivity of approximately 4 [S/m].
In general, a power transmitting device that wirelessly transmits/receives electric power has a coil including a conductor wire wound thereon several times. Application of alternating current power to this coil of this power transmitting device produces a magnetic flux that interlinks with the coil. This magnetic flux interlinking with the coil of the power receiving device causes induced current to be generated in the coil of the power receiving device. As a result of this, power transmission is performed.
Regarding the wireless technique, for example, Patent Document 1 discloses a technique in which a terminal device main body and a removable electronic device such as a memory card, perform electromagnetic induction type communication using wireless millimeter wave signals.
Patent Document 2 discloses a technique that uses electromagnetic induction in which an inductance value between the power transmitting device and the power receiving device is increased, using a magnetic body, to thereby increase the distance of electric power transmission.
Patent Document 3 discloses a technique that uses electromagnetic induction in which resonance (magnetic field resonance) is made at the same frequency, using a coil of a high Q value, to thereby improve mutual inductance between the power transmitting device and the power receiving device, and increase the distance of electric power transmission.